In the field of textiles it is often necessary to collect moist or wet multifilament continuous linear material into a "wet" wound package. But such practice, while necessary, gives rise to a myriad of difficulties since the linear material must eventually be dried.
For example, it has been the practice to protect glass filaments in glass filament forming operations by applying both water and a liquid sizing or other protective liquid to them before they are combined into a bundle or strand for collection into a wound package of wet glass strand. This practice requires subsequent package drying, and product problems ensuing from such drying. But the very nature of glass filaments demands application of a protective liquid before the filaments are combined into a strand; unprotected glass filaments tend to abrade each other upon contact. So processes forming glass filaments must apply a protectve coating to the glass filaments before combining them into a bundle.
Prior practices use bulk drying techniques to dry wet glass strand packages. This conventional drying takes a long time, and causes migration of solids in the sizing or coating to the periphery of the packages. Liquid moves outward to the periphery of the packages for evaporation; such movement tends to move solids to the periphery of the package. So solids tend to concentrate nearer the periphery of the package.
Consequently, strands from packages dried using prior bulk drying techniques have a nonuniform amount of solids along their lengths. And these strands are not fully satisfactory because the properties of the strands are not uniform along their lengths.
Dried packages of glass strand are ready for additional processing. The type of additional processing depends on the end use of strand. Glass strands suitable for textile application commonly pass through twisting and plying operations. Glass strands for use as a reinforcement for materials such as plastics may be combined into a multiple strand roving.
As one can appreciate, conventional package drying operations are cumbersome and not wholly satisfactory. Migration of solids effected during package drying produces a strand that does not have a uniform sizing treatment along its length. Then too, when wet strand collected into a package and subsequently dried, cohesive force of the sizing tends to cohere adjacent strands together. And this tends to cause strand breakage during subsequent processing when strand is withdrawn from the package.
There has been a pressing need for improvement.